For the purpose of preventing oxygen oxidation and performing long-term storing of various goods tending to be affected by oxygen and accordingly deteriorated or degraded, typified by, for example, food, beverages, pharmaceuticals and cosmetics, there have been used oxygen absorbents performing removal of oxygen in the packages containing these goods.
As oxygen absorbents, from the viewpoint of the oxygen absorbing capacity, easiness in handling and safety, there have generally been used oxygen absorbents including iron powder as the main reaction agent. However, such iron-based oxygen absorbents respond to metal detectors, and hence it has been difficult to use metal detectors for foreign matter inspection. Packages enclosing iron-based oxygen absorbents have possibility of ignition and hence cannot be heated with microwave ovens. In addition, iron-based oxygen absorbents take advantage of the oxidation reaction of iron powder, and hence have been able to develop the oxygen absorption effect thereof only for the objects to be stored which are high-moisture systems.
By constituting vessels with multilayer materials provided with oxygen absorbing layers composed of oxygen-absorbing resin compositions prepared by mixing iron-based oxygen absorbents with thermoplastic resins, packaging vessels have been developed in such a way that the gas barrier property of the vessels is achieved and the oxygen absorption function is imparted to the vessels themselves (see Patent Literature 1). However, such vessels also have a problem such that such vessels cannot be used for metal detectors, cannot be heated with microwave ovens, and can develop the effect thereof only for the objects to be stored which are high-moisture systems. In addition, such vessels suffer from a problem of insufficient internal visibility due to a problem of opacity.
From the aforementioned circumstances, oxygen absorbents including an organic substance as a main reaction agent are demanded. As the oxygen absorbent including an organic substance as a main reaction agent, an oxygen absorbent including ascorbic acid as the main agent is known (see Patent Literature 2).
On the other hand, an oxygen-absorbing resin composition being composed of a resin and a transition metal catalyst and having an oxygen-capturing property is known. For example, a resin composition is known which is composed of a polyamide, in particular a xylylene group-containing polyamide as an oxidizable organic component and a transition metal catalyst; in addition, a resin composition having an oxygen-capturing function, and an oxygen absorbent, a packaging material, a multilayer laminated film for packaging obtained by molding such a resin composition are shown as examples (see, Patent Literature 3).
As an oxygen-absorbing resin composition requiring no moisture for oxygen absorption, an oxygen-absorbing resin composition composed of a resin having carbon-carbon unsaturated bonds and a transition metal catalyst is also known (see Patent Literature 4).
In addition, as a composition to scavenge oxygen, a composition composed of a polymer including substituted cyclohexene functional group or a low molecular weight substance with the cyclohexene ring bonded thereto and a transition metal is known (see Patent Literature 5).